Distributed power train operation supplies motive power from a lead locomotive and one or more remote locomotives spaced apart from the lead locomotive in a train consist. Each lead and remote locomotive includes an air brake control system for controlling braking operations and a communication system for exchanging information between lead and remote locomotives over a communication link. A brake pipe fluidically interconnects each of the locomotives and rail cars of the train wherein modulation of a fluid flow, such as a fluid pressure in the brake pipe, is conventionally used to indicate desired braking operations. Brake application is typically accomplished by venting, or reducing a pressure in the brake pipe. However, brake pipe venting at only the lead locomotive of a train requires propagation of the corresponding brake pipe pressure reduction along the length of the train, thus slowing brake application at rail cars and remote locomotives near the end of the train. In distributed power trains, braking is more effectively accomplished by venting a brake pipe at both the lead and remote locomotives of the train, thus accelerating the brake pipe venting and the application of brakes throughout the train.
For distributed power trains with an operative communication link between a lead and remote locomotives, wireless traction and braking commands are typically transmitted to each remote unit over the link, such as when a train operator at the lead commands a brake application. For example, in response to a wireless brake application command, each remote locomotive also vents the brake pipe. Similarly, a brake release initiated at the lead is also communicated over the radio link, and each remote may respond by releasing its brakes and charging the brake pipe.
In the event that radio communication becomes inoperable in a distributed power train, it may be desired to command a remote locomotive experiencing a radio communication loss to enter a fail safe mode of operation, such as disabling charging or venting of the brake pipe at the remote, and/or reducing a traction condition of the remote. Such a fail safe state may be initiated by applying the brakes at the lead locomotive to generate a brake pipe brake application signal propagated along the brake pipe to the remote locomotive. For example, when a communication loss condition is indicated at a lead locomotive, such as via a communication loss indicator at a control panel of the lead locomotive, the operator of the lead locomotive may command a fail safe state by applying a minimum brake application to the train via the brake pipe. The minimum brake application signal propagated along the brake pipe from the lead locomotive is then interpreted as a command to suspend brake pipe charging and/or enter an idle traction state at the remote locomotive.